SUMMARY:

The method of designing the multilayer monolithic and prefabricated-monolithic linings of pressure tunnels and shafts of circular cross section, taking into account the work of linings combined with the rock mass, is considered in the paper. The linings of tunnels and shafts together with the surrounding mass are considered generally as multilayer deformable system. This method permits design of the lining for the internal head, external hydrostatic pressure, rock pressure, including tectonic original field of stresses and seismic actions induced by earthquakes. The method of designing takes into account the cracking in the concrete of linings and the surrounding rock mass under the effect of internal head. The procedure of optimum designing the lining subject to internal head is developed.

ZUSAMMENFASSUNG:

Im Vortrag wird eine Berechnungsmethode fuer mehrlagige monolitische und vorgefertlgt-monolitische Auskleidungen von Druckstollen und Druckschachten mit rundem Querschnitt behandelt, bei der die Zusammenarbeit der Auskleidungen mit dem Gebirgsmassiv beruecksichtigt wird. Der Stollen- und Schachtausbau wird zusammen mit dem umgebenden Massiv im allgemeinen als ein mehrlagiges verformbares System betrachtet. Die Methode ermöglicht es, eine Auskleidungsberechnung fuer Innendruck, hydrostatischen Aussendruck, Gebirgsdruck, darunter bei tektonischem Anfangsspannungsfeld, die durch das Erdbeben hervorgerufen werden, durchzufuehren. Die Berechnungsnethode beruecksichtigt die Bildung von Rissen im Beton und im umgebenden Massiv. Es ist eine methodik fuer die projektierung der Auskleidung fuer den Innendruck entwickelt worden.

RESUME:

Dans le rapport est exposee la methode de calcul des revêtements à plusieurs couches, monolithes et prefabriques-monolithes, pour les galeries et puits en charge de section transversale circulaire, qui tient compte du travail commun des revêtements avec le massif rocheux. Le revêtement des galeries et puits d''ensemble avec le massif ambiant est considere, dans le cas general, comme un systeme deformable à plusieurs couches. La methode permet le calcul d''un revêtement pour la poussee interieure, la pression hydrostatique exterieure, la pression de terrain, compte tenu aussi du champ de contrainte tectonique initial, et pour les effets dus aux seismes. La methode de calcul prend en consideration la formation de fissures dans le beton et le massit ambiant sous la poussee interieure. Une methode de l''etude de projet optimale de revêtement travaillant sous la poussee interieure a ete elaboree.

INTRODUCTION

High-pressure tunnels and shafts, as well as underground storage vaults for gas and oil, are usually built with linings of complex multiple-layer design, consisting of layers of steel, reinforced and prestressed concrete, tubing and other items. The complications are due to the high requirements made to such structures and the special features of their performance. Owing to their high cost it is of great importance to design such linings as precisely as possible, thereby reducing expenses in their construction.

The proposed method of designing the linings of pressure tunnels and shafts is based on the general method of designing multiple-layer sectional rings (Bulychev and 01ovyanny,1973) and deals with the lining and the surrounding rock massif as a single deformable system. Such an approach, typical for a new branch of the engineering sciences, the mechanics of underground structures (Bulychev,1982), in which rapid advances are being made in the USSR at the present time, enables the bearing capacity of the massif to be taken into account to the "maximum extent.

The design method is applicable for an arbitrary number of layers of a multiple-layer lining, including periodically nonhomogeneous layers containing annular stiffening ribs (flexible or rigid reinforcing members, tubing, etc.). The method imposes no restrictions on the thickness and mechanical characteristics of the layer materials. Design calculations can be carried out for linings subject to internal pressure, external hydrostatic pressure, rock pressure (including an anomalous tectonic initial stress field) and seismic action due to earthquakes (Bulychev,1979). The method takes into account the formation of cracks in the concrete and surrounding massif due to the internal pressure. A procedure has been worked out for optimal lining design for structures subject to internal pressure.

Computer programs have been developed for lining design.

THE THEORETICAL BASIS OF THE METHOD

The lining design method is based on the general method used for the design calculations of multiple-layer elastic rings, subject to external and internal loads, specified by Fourier series (Fig. 1) The essence of the method consists in determining the stresses on the contact surfaces between the layers by means of recursion formulas and load transmission factors (Bulychevand Olovyanny,1973). This approach excludes the need to formulate and solve systems of equations corresponding to the conditions of the contact surfaces between the layers, as required in the existing methods of multiple-layer lining design.

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